Question: What is the greatest common factor of $4$ and $18$ ? Another way to say this is: $\operatorname{gcf}(4, 18) = {?}$
Explanation: The greatest common factor is the largest number that is a factor of both $4$ and $18$ The factors of $4$ are $1$ $2$ , and $4$ The factors of $18$ are $1$ $2$ $3$ $6$ $9$ , and $18$ Thus, the greatest common factor of $4$ and $18$ is $2$. $\operatorname{gcf}(4, 18) = 2$